Bordetellae are Gram-negative bacteria that colonize the respiratory tracts of humans and animals. Bordetella bronchiseptica and Bordetella pertussis are well-adapted pathogens of the human and animal respiratory tract, respectively. Bordetella pertussis infects only humans and causes the acute respiratory disease known as whooping cough. It is estimated that 20-30% of adolescents and adults who have chronic cough lasting for more than one week are infected with B. pertussis. The current acellular vaccines, although effective against severe symptoms, are not particularly effective in preventing the carrier state. Adult and adolescent carriers harboring B. pertussis in the nasopharynx are responsible for the familial transmission of the bacteria to infants and young children, in whom the disease is severe and sometimes lethal. Thus, the continued presence of B. pertussis and B. parapertussis and the resurgence of pertussis despite widespread vaccinations, make the development of efficacious vaccines a top priority.
B. bronchiseptica has a broad host range infecting a variety of animals. It typically establishes asymptomatic infections but can cause atrophic rhinitis in pigs, kennel cough in dogs, snuffles in rabbits and bronchopneumonia in guinea pigs. Animals continue to be carriers of B. bronchiseptica despite vaccinations and frequently shed bacteria resulting in outbreaks among herds. Since B. bronchiseptica can cause respiratory disease in immunocompromized patients, vaccination of pets and food-producing animals with attenuated B. bronchiseptica may pose health risks to these patients through zoonotic transmission. Thus, there is a need to develop acellular vaccines for immunizing animals.